1. Field of the Invention
The present invention relates to a fuel injection internal combustion engine. More particularly, this invention relates to a spark ignition internal combustion engine having a sub-combustion chamber in which mixture gas with an air-fuel ratio adapted for an engine operating state over a wide operating range of the engine is supplied to a combustion chamber. The amount of hydrogen carbide discharged is lowered, and the engine has a high efficiency.
2. Description of the Background Art
A fuel injection internal combustion engine is known in which a sub-combustion chamber is provided in communication with a main-combustion chamber, and a mixture of the fuel and compressed air is injected to this sub-combustion chamber. For example, the Official Gazette of Japanese Patent Application Laid-open No. HEI 5-195787 describes such a fuel injection type two-cycle engine.
In the engine, according to FIG. 1 of the Official Gazette above, an air fuel injecting valve for injecting the mixture of the compressed air and fuel, and a spark plug, are fitted to the sub-combustion chamber. The air fuel injecting valve is provided with a solenoid type fuel switching valve and a solenoid type mixture switching valve.
In general, in such a fuel injection two-cycle engine, on the occasion of injecting the mist of fuel from the mixture switching valve, such spraying work is assisted by the pressure of the compressed air. Therefore, the fuel of comparatively high concentration is converted to fine particles to form the adequate spraying form (spraying condition of the fuel).
However, in order to constitute a desirable spray form, the compressed air must be maintained at a high pressure, for example, 5 kg/cm.sup.2 G or higher. More particularly, the pressure must further be increased in the case of supplying a large amount of fuel. In other words, since it is necessary to maintain the desirable spray form of the fuel, it is not easy to increase the amount of fuel to be supplied in the case of assisting the spraying effect of the fuel with low pressure compressed air. Moreover, a high pressure air pump and a high pressure fuel pump are necessary to assist the spray form of the fuel with the low pressure compressed air.
A spark ignition two-stroke cycle internal combustion engine is known which is provided with a sub-combustion chamber communicated with the main combustion chamber in order to make a positive ignition of a small amount of fuel under a low load operating state, and the mixture gas is formed in the sub-combustion chamber in a layer shape from rich mixture gas to lean mixture gas (refer to a gazette of Japanese Patent Publication No. Hei 5-195787).
In the case of the two-cycle internal combustion engine described in the aforesaid gazette, it had a disadvantage that a volume of the sub-combustion chamber was remarkably low as compared with a volume of the main combustion chamber, so that under a low load operating state, it was possible to form a small amount of fuel in the sub-combustion chamber in a stratified shape in a desired distribution of air-fuel ratio, although under a high load operating state, a large amount of fuel could not be supplied in the sub-combustion chamber in such a way that a proper air-fuel ratio might be attained. Therefore, irregular combustion was produced and a large amount of hydrogen carbide was discharged.